This invention relates to getter structures, and more particularly to getter structures that can be handled in ambient atmosphere during manufacture of enclosures receiving such getter structures.
Getter materials, that is materials which absorb gases and vapors, including water vapor, are well known and are used in a wide variety of enclosures to continuously absorb various gases and vapors, depending on the particular getter material employed, to either protect components located within the enclosure or to maintain a certain characteristic of the atmosphere within the enclosure, such as a dry atmosphere or a very low pressure atmosphere. One particular environment in which getter materials are used are vacuum insulation panels.
Vacuum insulation panels are known for various uses including use in refrigeration appliances where they greatly enhance the degree of thermal insulation within the cabinet of the appliance. Such panels must remain effective for the life of the appliance, generally a period in excess of 20 years. To do so, the panels must be highly gas impervious, yet must be able to prevent transmission of heat not solely by conduction and radiation through the panels, but also by conduction along the surface of the panels. Further, any gases and vapors that do permeate the panel walls in excess of what is tolerable, depending on the panel filler insulation material, must be absorbed or otherwise captured to prevent degradation of the panels which, for insulation purposes, are most effective only when the interiors of the respective panels are evacuated to a very low pressure by removal of all gases and vapors (the desired vacuum level depends on the specific filler insulation material).
U.S. Pat. No. 2,863,179 discloses a multi-compartment insulation material for refrigerators. An inner bag seals a fibrous material in an insulating gas filled environment, and is intended to prevent the insulating gas from escaping. An outer bag contains the inner bag and an adjacent layer of fibrous insulation. The purpose of the outer bag is to prevent moisture and air from entering the inner bag, and to minimize abrasions caused by handling, however, the inner bag is not shielded from atmospheric pressure.
It is important in the construction of vacuum thermal insulation panels to prevent the vacuum within the panels from being deteriorated and eventually lost due to slight permeability of the walls of the panel. Therefore, as is known in the art, "getter" materials are placed within the panel to absorb various gases including oxygen, water vapor, nitrogen, etc. Use of such getter materials in vacuum insulation panels is known and is disclosed in U.S. Pat. Nos. 4,000,246; 4,444,821; 4,668,551; 4,702,963 and 4,726,974. Each of said patents discloses the use of a getter material in a single compartment of a vacuum insulation panel. A problem resulting from the use of such getter materials is that some getter materials may absorb more than one type of gas and thus may be consumed by a relatively prevalent type of gas, such as water vapor, and thus would not be available to absorb other gases, while less expensive materials should be used for absorbing water vapor. Once the getter materials have been consumed, degradation of the panel will begin.